A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned.
Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
For scanning or stepping, the patterning device and/or the substrate need to be moveably supported. In a conventional lithographic apparatus, a patterning support and/or a substrate table are supported by an actuator assembly which includes a first and a second actuator part. In a conventional actuator assembly, the first actuator part includes two magnets for generating a magnetic field in a gap between the magnets. A second actuator part includes a coil, which coil is positioned in the gap between the magnets in order to position the coil in the magnetic field. Thus, the magnets of the first actuator part are positioned on opposite sides of the coil of the second actuator part.
Since the magnets of the first actuator part are positioned on opposite sides of the second actuator part, assembling and mounting of the actuator assembly may be difficult. If the actuator assembly malfunctions, it may be necessary to disassemble the actuator assembly, i.e. dismounting at least one of the actuator parts, for inspection, repair or replacement. Thereafter, the assembly has to be assembled and mounted again. Disassembling and assembling an actuator assembly in a lithographic apparatus is even more complicated than the initial assembling and mounting, since the actuator assembly is then surrounded by a number of other parts of the lithographic apparatus, limiting the working space. Disadvantageously, it may therefore be needed to design the lithographic apparatus such that extra space around the actuator assembly is provided for easy accessibility, inspection and fast repair.